1,1,1-Trichloroethane is a widely used industrial cleaning solvent. With the recent restrictions placed on the use of trichloroethylene, as for example, vapor degreasing, more people are substituting 1,1,1-trichloroethane into uses to which the trichloroethylene was employed. Many of these uses place a severe stress on the 1,1,1-trichloroethane. Previous inhibitor systems for the 1,1,1-trichloroethane have been found weak or ineffective in protecting the solvent and/or the parts being cleaned. Thus, it is necessary to find new inhibitor systems for the 1,1,1-trichloroethane which will permit the extended uses industry is making of this useful solvent.
The prior art has added numerous members from most classes of organic compounds in attempts to improve the stability of 1,1,1-trichloroethane to degradation in the presence of heat, metals (particularly aluminum) and water. For example, esters, ethers, amines, cyano compounds, alcohols, ketones, aldehydes and the like have been suggested alone and in combination in the literature and in patents. However, commercial grades of 1,1,1-trichloroethane used in the major industrial countries contain at least one inner ether (an epoxide and/or dioxane, dioxolane, or trioxane), usually a nitroalkane (nitromethane and/or nitroethane) then one or more of the following acetylenic alcohol, nitrile (acetonitrile or .beta.-methoxypropionitrile), ortho ester (trimethyl ortho formate), lower alkanol (t-butyl or t-amyl alcohol), a ketone (methyl ethyl ketone). These compounds account for the components used in the main in the present day inhibitor systems.
One of the largest suppliers used dioxane, nitromethane and butylene oxide for years. However, even this recognized superior system has shown weaknesses in certain fields of use wherein trichloroethylene was previously employed. Such weaknesses are a result of operator's lack of care in maintenance of their equipment, a chore not usually undertaken on a regular basis when trichloroethylene was employed. However, any rusting, heavy metals fines, particularly aluminum, grinding and buffing compounds, lubricant oils and fluxes such as employed in miniature printed circuits increase the degradation of the solvent and create corrosive atmospheres which attack the metal parts being cleaned. In the past, the manufacturers have been able to screen the new uses and monitor the uses. Such is not possible with the widespread usage to which the solvent has been put in recent months.
It is, therefore, an object of the present invention to provide a stabilized grade of 1,1,11-trichloroethane suitable for the severe use conditions encountered in the substitution of 1,1,1-trichloroethane for trichloroethylene